Hot liquid or vapor generator



Oct. 6, 1959 I G. STABENOW 2,907,306

HOT LIQUID 0R VAPOR GENERATOR Filed Jan. 12, 1955 3 Sheets-Sheet l INVENTORZ GeazySiafienow,

PM PM A TTORNEYS.

Oct. 6, 1959 G. STABENOW HOT LIQUID OR VAPQR GENERATOR Filed Jan. 12, 1955 3 Sheets-Sheet 2 m 67' FROM com [070R INVENTOR. 620/9 Siam/20a) BY FMQ PML ATTORNEYS.

' HQT LIQUID OR VAPOR GENERATOR Filed Jan. 12, 1955 3 Sheets-Sheet 3 v INVENTOR. GemgSzabe/mw,

- Pwfiwi ATTORNEYS.

United States Patent ice invention. relates to generators, and more particu- Iarly to forced. recirculation heatersi or boilers for heatingor vaporizing. liquids such as water, Dowtherm and thelike- Y i It is conventional. in the-steam generator art to deliver steam and boiler feed water into a steam. drum and to recirculate water from the steam drum by means of a pump or the like for returning the water to the steam generating portion of the boiler. Heretofore, the recirculated water has been introduced into the boiler tubes. his well known that heat exchangers may be located in the stack or elsewhere in the path of the exhaust gases from the boiler and that feed water may be "circulated through the heat exchanging means in order to heat the feed water. This arrangement results in a reduction of the stack temperature and improves the overall thermal 'efiiciency of the boiler.

It is an object of this invention to improve further the operating eificiency of steam or other generators.

Still another object of this invention is to provide a means. for separating water from the steam produced by the steam generator and for recirculating the water and for utilizing the heat content of the stack gases to pro-heat the recirculated 'water before the recirculated water is introduced into the steam generator.

, It has been discovered that it is advantageous to recirculate boilerwater through a pre-heater and then upwardly through steam generator tubesto an upper header, and from that upper header downwardly through a plurality of boiler tubes arranged in parallel. Since thewater flowing downwardly through the boiler tubes has been extensively heated prior to its movement downwardlyin the boiler tubes, and since the corresponding boiler tubes are often exposed to the direct heat of the hot combustion productg there is a tendency for the water to vaporize as it flows downwardly in the tubes. Since the vapor has the tendency to rise, and since the water is moving downwardly, the formation of the vapor impedes the water flow. Moreover, the extent of the interference with fluid flow varies with the intensity of the heat applied to each boiler tube. Since the tubes are connected in parallel to upper and lower headers, the water tends to take the course of least resistance, increasing flow in the cooler tubes and decreasing flow in the hotter tubes. This eventually results in severe reduction of water flow in the. hottest tubes, which tend to overheat, further impeding the water flow, causing proportionally more water to flow downwardly through the cooler tubes, and eventually results in failure of the tubes which are exposed to the hottest combustion products.

'It is an object of, this invention to overcome the foregoing'difiiculty. Another object of this invention is to provide a novel steam generator-wherein wateris sepa'rated from the steam produced and is recirculated, at a new rate considerably in excess of the quantityofsteam generated, through the boiler for ultimate flow down- 2,907,306 Patented Oct.-6, 1959 wardly through parallel boiler tubes from an upper header to a lower header, and wherein the rate of flow of the water downwardly through the boiler tubes does not vary substantially from tube to tube. Other objects and advantages of this invention, including the simplicity and economy of the same, will further become apparent hereinafter and in the drawings whereof-z V Fig. l is a vertical sectional view of one specific form of steam boiler embodying features of this invention;

Fig. 2. represents a partial view in perspective illustrating the arrangement of the tubes of the steam gen erating portion of the boiler, with certain parts removed and others broken away in order more particularly to illustrate important features of this invention;

Fig. 3 represents a vertical sectional view through one of the upper headers of the steam generating portion of the boiler illustrated in Figs. 1 and2; and

Fig. 4 represents an enlarged sectional view taken as indicatedby the lines and arrows IV-IV which appear in Fig. 3-. r V

Turning now to the specific embodiment of. the inven tion selected for illustration in the drawings, Fig., 1 shows a boiler having a steam generating portion or furnace 11 and a convector portion 12. a I

The furnace 11 has a front Wall 13 and is bounded rearwardly by a bridge wall 14 which extends laterally between the side walls 15. Located at the lower por-' tion of the front wall1-3 is a burner. 9, which maybe an oilburner or gas burner, for example. The: burner 9 produces hot combustion products in the steam gen erator portion 11 of the boiler, which combustion,prod ucts convert water to steam. The construction and operae tion of suitable oil or gas burners is well known in the art, and is not of itself a part of thisinvention. Accordingly, theconstruction of the burner 9 is not illustrated in further detail in the drawings. Bridge wall 14 extends upwardly from the level 16 of the. boiler floor and terminates at a level 18 which is spaced below the level of the top 20 of the boiler, providing intervening free space 17 through, which the combustion products flow. I

The convector portion 12 extends rearwardly from the bridge wall 14 to a back wall 21. Intermediate the walls 14, 21 is a partition wall 22 which extends down from the top 20 and terminates at a level 19 which is spaced above the level of the floor 16 and provides free space 23 through whichthe combustion products flow.

The partition wall 22 divides the convector portion 12 of the boiler into two portions, a first convector space 24 and a second convector space'25, and provides a passage below the partition wall. through which hot combustion products flow from one convector space to the other. The convector space 24 is in communication with the steam generator portion 11, while the second convector space 25 is connected to a stack 26 for disposition of the combustion products.

Arranged generally vertically and in parallel with one another are a plurality of steam generator tubes 31, which extend from upper headers to lower headers in the steam generator portion 11 of the boiler. It will be appreciated from Figs. 1 and 2 that the steam generator tubes 31 are arranged in four groups vwhich are located adjacent to the front wall 13, side walls 1 5 and bridgewall 14: The tubes adjacent the front wall 13 are. referred to collectively as the front water wall 32. The "tubes ad'- jacent to the side walls 15 are referred to as the side water walls 33, and the tubes adjacent to the bridge wall 14 are referred to as the bridge waterwall '34.

It will be appreciated that the bridge water. wall 34 is located in the direct path of the combustion products from the burner 9; The combustion products are 'concentrated on the water 'wall 34 in the area adjacent the bridge wall 14. The water flowing through the boiler tubes protects the bridge wall 14 from the intense heat of the flame and also protects the tubes themselves as will further become apparent hereinafter.

Located in the convector spaces 24,25 are a plurality of groups of convector tubes 36 which are spaced apart from'one another providing intervening spaces through which the combustion products flow. The convector tubes 36 in the second convector space 25 are connected into a bottom header 37 which is connected to the tubes at the bottom of first convector space 24. A header 39 connected to the upper ends of the convector tubes 36 in first convector space 24 is connected to a pair of pipes 40 which communicate with an upper header 41 above the steam generator portion 11 of the boiler. The upper header 41 is connected to the tops of the tubes of the bridge water wall 34. At the bottom of the bridge water wall 34 the tubes are connected to a bottom header 42 which communicates with the bottoms of some of the tubes of the side water walls 33, but the bottom header 42 terminates at 43, 43. The tubes in the portions of the side water wall 33 with which the header 42 communicates are designated by the numbers 33a. The upper ends of the tubes 3311 are connected to upper side wall headers 44 into which are connected the upper ends of the remaining side wall tubes 33b. The bottoms of the side wall tubes 33b are connected into a header 45 which is connected into the bottoms of the tubes of the front water wall 32. At the upper ends of the tubes of the front water wall 32, these tubes are connected into a header 46 which is connected by a pipe 47 into a steam drum 50. The steam and residual water are separated in the steam drum 50, and feed water is introduced at 48 into the steam drum, all in accordance with the procedures well known in the art. A recirculation pipe 51 is connected into the water portion of the steam drum 50 and extends to the inlet end of a motor-driven forced recirculation pump 52. The outlet of pump 52 is connected into a pipe 53 which is connected in turn to a top header 54 which communicates with the upper ends of the convector tubes in the second convector space 25.

It will accordingly be appreciated that means are provided for forming hot combustion gases which convert water to steam, for separating water from the generated steam, and for recirculating the separated water through heat convectors which are in contact with the exhaust gases from the combustion space, prior to the re-introduction of the recirculated water into the steam generating portion of the boiler. This is an important and advantageous feature of this invention and materially improves the overall efliciency of the'boiler.

I Turning now to Figs. 2-4 of the drawings, it will be appreciated that the fluid flowing into the header 41 from pipes 40 is recirculated water whichhas been subjected to the heat of the combustion gases in the convector spaces 24, 25. It will further be appreciated that the water flows downwardly through the boiler tubes in the bridge water wall 34. It will further be appreciated that the most intense heat from the burner or burners is focused on certain localized areas in the bridge wall, such as the area indicated by the dot-dash lines 35 in Fig. 2, tending to heat some of the tubes more than other tubes. In areas where particularly intense heat is applied, the heat tends to vaporize some of the water in the tubes, thereby forming steam bubbles which tend to flow upwardly or countercurrent to the desired flow of water. This creates a resistance to the flow of water in certain of the tubes, whereupon the water takes the course of least resistance and tends to flow in greater volume down the cooler tubes. As a result, the central tubes illustrated in Fig. 2 tend to become progressively hotter, and to produce more and more steam bubbles, eventually causing failure of one or more of the central tubes.

In accordance with this invention, the foregoing difiiculty is overcome by inserting an orifice device 55 in the top only of each of the steam generator tubes of the bridge water wall, where the tubes are connected into the upper header 41, and at the tops only of all other steam generator tubes which are arranged in parallel to convey water downwardly from an upper header to a lower header. As shown in the drawings, no orifice device is inserted at the lower ends of the steam generator tubes.

Figs. 3 and 4 illustrate one specific form of orifice which may be utilized in accordance with this invention. The orifice per se is not a part of the present invention, but is disclosed and claimed in my co-pending patent application, Serial No. 460,914, filed October 7, 1954, which is abandoned.

In accordance with this invention, orifices as hereto fore described are inserted into the boiler tubes of upper headers wherever it is intended to pump water downwardly through tubes which are arranged in parallel and which extend from an upper header to a lower header, and in which water is to flow downwardly. Figs. 3 and 4 disclose orifices which are installed in that portion of the upper header 44 which communicates withthe side wall tubes 3312. It will be appreciated, of course, that the header orifice structures in the header 41 may be, and preferably are, identical to the orifice structures in the header 44. v

From Figs. 3 and 4 it will be appreciated that the end portion of each steam generator tube 31 extends through an opening into the header 44. The tube 31 has a flared end 60, sealing the tube to the header. The number 61 designates a substantially cylindrical strainer tube having a plurality of spaced circular holes 62 through which boiler water may flow. The strainer tube 61 has a tapered front end 63 which is frictionally engaged with the flared end 60. An apertured disc 64, preferably consisting of stainless steel, extends across the outlet end of the strainer tube 61. The disc 64 comprises an orifice member which lies in a plane substantially perpendicular to the longitudinal central axis of the strainer tube 61 and boiler tube 31. The orifice member 64 has a central circular opening 65 through which steam or water flows. I i

The size of the opening 65 is related in a predetermined manner to the rate of flow of water through the tubes and the potential drop or head of water between the upper header and the lower header, so that the pressure drop of the water flowing through the opening 65 is greater than the head of water between the upper and lower header. L If, for example, vaporization should occur in a single tube of the series, the pressure effect of the hydraulic head of the tube would be at least partially lost, but with the orifice present its pressure drop would still be more than equivalent to the fluid heads of the other tubes of the series. Thus, there is positive assurance that there will always be a greater pressure on the top of a tube than the back-pressure due to the heights of the water columns of the other tubes of the series, even when vaporization has started to take place in a single tube. This fact assures that there will always be down-flow of liquid in ali tubes, which in turn assures that an incipient vaporization will be halted before it can develop into the creation of a hot spot.

Accordingly, it will be appreciated that, notwithstanding the fact that the recirculated water has already been heated in the convection heaters in spaces 24 and 25, it does not vaporize in a manner to impede downfiow of water. The downwardly flowing, hot boiler water is apportioned by the orifices in header 41 and distributed uniformly to the individual boiler tubes of the bridge water wall 34. This apportionment is achieved by neutralizing any localized tendency toward reverse flow in any individual tube which is exposed to the intense heat of the burner flame, all ashas been described in more particular detail above. The words apportioning and apportionment are not intended to imply a distribution in exactly equal proportions, since the relative quantities of fiow may vary somewhat from tube to tube and from time totime. However, when the downwardly directed flow in any given tube tends to stop or to slow down greatly with respect to the flow in the other tubes, the operation of the orifices tends to increase the rate of flow into that tube with respect to the rate of flow into the other tubes of the series, and the foregoing words are intended to apply to such relative increase. Even intense heat, directed on a relatively small area of the bridge water wall, is insufiicient to impede the downflow of water enough to damage the tube. And the restrictive means of this invention is similarly effective at the top of side water wall tubes 33b, even though the water has previously been heated in the convectors as well as the bridge water wall 34 and side water wall 33a.

It is particularly important to note that the water passes downwardly through at least two tube sections. It passes through the orifices at the top of the bridge wall 34 and consumes a certain amount of pressure to overcome any vapor formation in that section of the tubing, and then after passing upstream in the side water wall section 33a, it flows into the upper header. At this point the water flows through a second group of orifices at the top of side water wall 33b and flows downwardly through that side water wall for ultimate discharge through the front water wall back into the drum. Accordingly, it will be apparent that orifices are provided in series relation in the circuit, as well as in parallel. This is an important and advantageous feature of the invention.

It will be appreciated that various modifications may be resorted to without departing from the scope of this invention. For example, the convector section may consist of one, two, or any other number of separate sections and various tube arrangements may be utilized. It will also be appreciated that, although the headers 42, 45 are shown as separate headers, they may quite desirably be fabricated in the form of a single, one-piece header, with blanks at appropriate locations dividing the fluid flow as desired.

It will further be appreciated that equivalent means may be substituted for those shown in the drawings, that parts may be reversed, and that certain features of this invention may be used independently of other features, all within the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In a generator for continuously heating a liquid circulated therethrough and producing vapor therefrom, a furnace section, a plurality of sections of upflow and downflow liquid carrying liquid tubes which are exposed to hot combustion gases in said furnace section, said sections being connected in series, the tubes of each section being of equal length and arranged in parallel and extending from an upper header to a lower header into each of which the liquid tubes are connected, said downflow sections having heating surfaces substantially equivalent to the heating surfaces of said upflow sections, restrictive orifice means adjacent the top only of each of said downflow tubes where it is connected to said upper header, the bottoms of said tubes being open and free of any such restrictive orifice means, pumping means for introducing said liquid at a predetermined rate into the upper header of each section of downflow tubes for flow in parallel downward through all of said restrictive orifice means and then downward through all of said downflow tubes and into the lower header thereof and for introducing liquid at a predetermined rate into the lower header of each section of upflow tubes for flow in parallel upward through all of said upflow tubes and into the upper header thereof, said restrictive orifice means being connected in parallel in each section of downflow tubes and in series with respect to the sections and each said restrictive orifice means having an opening which is of less area than the area of the corresponding tube and which has an area providing a pressure drop which is greater than the pressure drop of the entire length of the boiler tube in which it is located.

2. In the generator of claim 1 a convector section, a bridge wall separating said convector section from said furnace section, heat exchange tube means disposed in said convector section and connected in series to the tubes in said furnace section and pipe means connecting said heat exchange tube means and the tubes in said furnace section in series, said pumping means further comprising means for pumping said liquid serially through said heat exchange tube means, said pipe means and the tubes in said furnace section.

3. In a generator for continuously heating a liquid circulated therethrough and producing vapor therefrom having a roof, a floor, front and back walls and side walls forming a chamber, the novel combination comprising a bridge wall extending laterally between the side walls and from the floor to a point spaced from the roof dividing the generator into two communicating portions, said portions being a furnace portion and a convector portion, a burner disposed in the lower part of said front wall, a partition wall in said convector portion extending laterally between the side walls, depending from the roof and extending downward to a point spaced from the floor, a flue in the roof of the convector portion adjacent the back wall, said bridge wall and said partition wall forming baffle means for guiding the products of combustion of said burner from the burner to the flue, heat exchanger tube means vertically disposed in said convector portion on both sides of said partition wall, boiler tube means disposed in said furnace portion, said heat exchanger tube means and boiler tube means each comprising a plurality of sections of upflow and downflow liquid tubes operatively connected in parallel to upper and lower headers, the downflow sections of said boiler tube means having heating surfaces substantially equivalent to the heating surfaces of the upflow sections of said boiler tube means, each of the downflow liquid tubes in the boiler tube means having restrictive orifice means at the upper end thereof having an opening which is of less area than the area of the corresponding tube and which has an area providing a pressure drop which is greater than the pressure drop of the entire length of the boiler tube in which it is located, separator drum means disposed outside said chamber for separating the circulated liquid from the vapor produced therefrom, liquid forcing means disposed outside said chamber and connector pipe means disposed outside said chamber for operatively connecting consecutively in series said liquid forcing means, said heat exchanger tube means, said boiler tube means, said separator drum means and said liquid forcing means, said liquid forcing means comprising means for forcing the liquid to be heated through said connector pipe means upward and downward through said heat exchanger means, upward and downward through said boiler tube means, through said separator drum means and through said connector pipe means to said liquid forcing means.

References Cited in the file of this patent UNITED STATES PATENTS 1,538,256 Munzinger May 19, 1925 1,545,668 La Mont July 14, 1925 1,732,428 Bell Oct. 22, 1929 1,860,364 La Mont May 31, 1932 1,932,918 Abendrott Oct. 31, 1933 1,988,659 La Mont Jan. 22, 1935 2,170,345 Bailey Aug. 22, 1939 2,316,762 Bailey Apr. 30, 1943 

